The present invention relates to a separator for sorting particulate material into coarse and fine fractions, e.g. raw materials of cement or cement clinker or similar mineral raw materials which have been ground under high pressure in a roller press, resulting in that the ground material contains agglomerates which have to be desagglomerated before the material can be further treated.
Separators for sorting out a fine fraction from a coarse fraction of ground, particulate material are disclosed e.g. in the form of air separators in i.a. AU patent No. 220,069, DE patent No. 1,913,946, EP patent specification No. 0,023,320 and EP patent specification No. 0,210,729 and in Duda: Cement Data Book 1, chapter 15 (3rd edition, Bauverlag GmbH, Wiesbaden and Berlin, 1985). When using such air separators in their present form of single separators in connection with roller presses, the material charge has usually been subjected to a separate desagglomeration process, e.g. in a hammer mill, prior to the separation process in order to disintegrate the agglomerates, which entails an increase in the number of individual machines in the grinding plant and wear and tear of the hammer mill. The inevitable dust formation in the hammer mill causes dust-laden material to be conveyed to the separator.
As a continuously increasing part of the grinding tends to take place in the roller press this furthermore results in that the separator has to treat a continuously increasing amount of material due to an increase in the closed-circuit rate. As a result the material concurrently becomes coarser which again results in increased wear and tear and an even higher power consumption in the separator.
When subsequently using a tube mill in such prior art single separator plants to comminute the separated roller-pressed material charge into fine particles, the material supplied to the tube mill has up to now either been characterized in containing large single particles, which require large grinding bodies in the tube mill, or the tube mill has been fed with semi-ground material of a relatively high fineness, resulting in the dry material tending to clog in the tube mill.
Further, from EP-A2-0250747 a double separator of the air separator type is known for sorting particulate material suspended in a conveying gas, where the double separator comprising an upper coarse separator coupled in series with and directly connected to a lower fine separator. Both the upper and lower separators are provided with rotors rotating about vertical shafts, each rotor having adjustable louvre blades. The upper, coarse separator being a horizontal, centrifugal impact pulveriser having arms for disagglomerating coarse material containing agglomerates From a crushing device, such as a roller mill, the material load of which is charged to the separator through an inlet duct mounted in the upper part of the coarse separator; space is provided between the arms of the impact pulverizer allowing the separated parts of the coarse fraction suspended in the conveying gas to be passed through the separator housing into the lower separator For Further treatment in same.
Compared to the previously mentioned single separator plants, the double separator according to EP-A2-0250747 only differs from these in having the external disagglomerator, such as a separate hammer mill, replaced by the upper coarse separator functioning as a built-in desaggtomerator, for which reason the use of this double separator in principle entails the same disadvantages as described in connection with the single separator plants.
It is therefore the object of the present invention to provide a separator which can be used together with a roller press and optionally together with a tube mill and in which the above mentioned drawbacks are avoided.